The present invention relates to a maintenance device for performing maintenance on an elongated, and in particular tubular, hollow body which is designed to transport a fluid, having a sealing device which has a function-performing unit, which is intended to seal off a working region from the surroundings of the hollow body, and which can be moved in one direction along a surface of the hollow body. The invention also relates to a method of making a maintenance access for a hollow body as described above, and in particular for a pipeline for transporting gas, water or oil for example.
A device of the aforementioned kind is known from EP 0 935 089 B1. Described in this document are a device and a method for cutting into a pipeline in which a housing of a sealing device, which also comprises an adapter, is moved at right angles to the longitudinal extent of the pipeline and thus over the surface of the pipeline. The sealing device is seated on the pipeline with a seal. The housing, which has a function-performing unit which takes the form of a cutting tool, seals off from the surroundings of the pipeline the working space which is situated between the two parts of the adapter, which are removed from one another in the longitudinal direction. By opening or removing the housing, the working space or region becomes accessible. A cut is made by the function-performing unit during the movement. Then a gate valve is introduced into the pipeline through the region milled out by the tool in order for example to seal off the pipeline. With the device described, it is only short individual cuts which are made in a pipeline or circular openings matching the size of the boring or drilling tool. There are thus limits to the shape of an opening for maintenance access. For complete sections of a pipe to be removed, the device would have to be re-fitted, in which case the pipeline would have to be cut twice around its circumference. The region which had already been cut might be exposed when this was done, as a result of which a procedure of this kind cannot be performed, in the way which is often desirable, while a pipeline continues in operation. What is more, the pipeline might become unstable, because the maintenance device is not intended to make a complete cut in the pipeline.
It is an object of the present invention to provide a maintenance device and a method for making a maintenance access which are an improvement on the prior art.